The application relates to a hearing device comprising a) first and second input transducers for picking up sound signals from the environment and providing first and second electric input signals, b) a first and signal strength detectors for providing signal strength estimates of the first and second electric input signal, the first input transducer being located at or behind an ear of the user, and the second input transducer being located at or in an ear canal of the user. The hearing device further comprises c) a signal processing unit providing a processed signal based on the first and second electric input signals, and d) an output unit comprising an output transducer for converting the processed signal or a signal originating therefrom to a stimulus perceivable by said user as sound. The hearing device further comprises e) a feedback detector comprising e1) a comparison unit operationally coupled to the first and second signal strength detectors and configured to compare the signal strength estimates of the first and second electric input signals and to provide a signal strength comparison measure indicative of the difference between the signal strength estimates, and e2) a decision unit for providing a feedback measure indicative of current acoustic feedback from the output transducer to the first and/or second input transducers based on the comparison measure. In an embodiment, the feedback measure is used to control processing in the signal processing unit, e.g. a beamformer unit and/or a feedback cancellation system, and/or an amplification unit. The invention may e.g. be used in hearing aids, in particular hearing aids comprising an ITE-part adapted for being located at or in an ear canal of a user and a BTE-part adapted for being located at or behind an ear or the user.
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1. A hearing device adapted for being arranged at least partly on a user's head or at least partly implanted in a user's head, the hearing device comprising
an input unit for providing a multitude of electric input signals representing sound,
a signal processing unit providing a processed signal based on one or more of said multitude of electric input signals, and
an output unit comprising an output transducer for converting said processed signal or a signal originating therefrom to a stimulus perceivable by said user as sound;
the input unit comprising
a first input transducer for picking up a sound signal from the environment and providing a first electric input signal, the first input transducer being located on the head of the user;
a second input transducer for picking up a sound signal from the environment and providing a second electric input signal, the second input transducer being located at or in an ear canal of the user, the hearing device further comprising
a feedback detector comprising
a first signal strength detector for providing a signal strength estimate of the first electric input signal for each of a plurality of frequency bands, and
a second signal strength detector for providing a signal strength estimate of the second electric input signal for each of the plurality of frequency bands,
a comparison unit operationally coupled to the first and second signal strength detectors and configured to compare the signal strength estimates of the first and second electric input signals and to calculate a difference between said signal strength estimates of the first and second electric input signals as a signal strength comparison measure for each of the plurality of frequency bands;
a weighting unit comprising a mixer or a beamformer unit, the mixer or beamformer unit providing a mixed or beamformed signal based on a weighted combination of said multitude of electric input signals or signals derived therefrom,
wherein the hearing device is configured to control the weights applied by the mixer or beamformer unit on the first and second electric input signals or signals derived therefrom in dependence of the signal strength comparison measure calculated from the signal strength estimates of the first and second electric input signals for each of the plurality of frequency bands, such that the weight of the first electric input signal is increased and/or the weight of the second electric input signal is decreased in the mixed or beamformed signal in each of the plurality frequency bands in which the signal strength comparison measure indicates that the current acoustic situation is dominated by feedback.
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a decision unit for providing a feedback measure indicative of current acoustic feedback from said output transducer to said first and/or second input transducer based on said signal strength comparison measure for each of the plurality of frequency bands, and
wherein the hearing device is configured to control the weights applied by the mixer or beamformer unit in dependence of the feedback measure for each of the plurality of frequency bands.
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The present application relates to hearing devices, e.g. hearing aids. The disclosure relates specifically to a receiver-in-the-ear (RITE) type hearing device comprising a microphone system comprising a multitude (two or more) of microphones, wherein at least a first one of the microphones is adapted to be located at or in an ear canal of a user, and a second one of the microphones is adapted to be located a distance from the first one, e.g. at or behind an ear (pinna) of the user (or elsewhere). The present disclosure proposes a scheme for identifying dominant acoustic feedback from a receiver (loudspeaker) located in the ear canal to the microphone system. An embodiment of the disclosure provides a hearing aid with one or more microphones located behind the ear and with one or more microphones and a loudspeaker located in the ear canal.
Embodiments of the disclosure may e.g. be useful in applications such as hearing aids, in particular hearing aids comprising a second input transducer adapted for being located at or in an ear canal of a user and a first input transducer located elsewhere on the users' body, e.g. in a BTE-part adapted for being located at or behind an ear or the user.
An object of an embodiment of the present application is to detect situations in a hearing device where acoustic feedback is substantial or dominant. In particular, it is an object of embodiments of the disclosure to detect feedback in so-called open fittings, e.g. in a hearing device comprising a part (termed the ITE-part) adapted for being located in the ear canal of a user, wherein the ITE-part does not provide a seal towards the walls of the ear canal (e.g. in that it exhibits an open structure, such as in that it comprises an open dome structure (or an otherwise open structure with relatively low occlusion effect) to guide the placement of the ITE-part in the ear canal). It is a further object of embodiments of the disclosure to detect feedback in a hearing device comprising a mould intended to allow a relatively large sound pressure level to be delivered to the ear drum of the user (e.g. a user having a severe-to-profound hearing loss).
According to the present disclosure, a hearing device is provided. The hearing device comprises a first microphone located at or in an ear canal of a user, e.g. in or together with a speaker unit (also located in the ear canal), and a second microphone located behind an ear, e.g. in a BTE-part (BTE=behind-the-ear) of the hearing device. Such style is in the present application termed M2RITE (intended to indicate the presence of 2 microphones (‘M2’) in a receiver-in-the ear (RITE′) type of hearing device). This results in a relatively large distance of 35-60 mm between the first and second microphone (cf. e.g.
The acoustical feedback to the microphones located in the ear canal and at or behind the ear from a receiver located in the ear canal will be in the (acoustic) near-field range.
So, according to the present disclosure, if the level difference of a signal between the two microphones is less than a feedback difference threshold value, e.g. 15 dB, then the sound is not caused by feedback, and if the level difference is higher than the feedback difference threshold value, e.g. 15 dB, then it can be expected to be feedback.
In the conventional BTE, RITE or BTE this will not be possible to detect so clearly.
A Hearing Device Comprising a Feedback Detector:
In an aspect of the present application, an object of the application is achieved by a hearing device, e.g. a hearing aid, adapted for being arranged at least partly on a user's head or at least partly implanted in a user's head, the hearing device comprising
The hearing device further comprises
This has the advantage of improving feedback detection.
In an aspect, a hearing device comprising a feedback detector is provided.
In an embodiment, the feedback measure is implemented as a binary value (e.g. 0 or 1). In an embodiment, the feedback measure is implemented as a relative measure (e.g. between 0 and 1).
In an embodiment, the feedback measure is used to control processing in the signal processing unit, e.g. a beamformer unit and/or a feedback cancellation system, and/or an amplification system. In an embodiment, the feedback measure is used to control or influence a weighting unit for providing a weighted combination of a number of electric input signals representing a sound from the environment of the user wearing the hearing device. In an embodiment, the feedback measure, and/or the weights wi are frequency dependent. Thereby signal content of a resulting signal (being a weighted combination of the electric input signals) may be differently weighted at different frequencies. In an embodiment, the weighting unit provides a signal that is a linear combination of input signals INi (i=1, . . . , M): IN1(k,m)*w1(k,m)+ . . . +INM(k,m)*wM(k,m), where wi. i=1, . . . , M, and M is the number of input transducers (ITi), e.g. microphones, and thus corresponding electric input signals (INi), and where k and m are frequency and time indices, respectively. The weights wi are real or complex (and in general, time and frequency dependent) weights. The weighting unit may implement a selector (in which case the weights wi are binary, one of the weights being equal to is 1, and the others being equal to 0), or a mixer (in which case the weights wi are real and the sum of the weights is 1), or a beamformer filtering unit (in which case the weights wi are complex). In an embodiment, the feedback measure is used to determine the weights wi.
In an embodiment, the attenuation of the acoustic propagation path of sound from the second to the first input transducer is determined for an acoustic source in the near-field, e.g. from the output transducer of the hearing device as reflected by the ear drum and leaked through the ear canal to the second input transducer. In an embodiment, the propagation distance between the output transducer (or the outlet from the output transducer) and the second input transducer is less than 0.05 m, such as less than 0.03 m, e.g. less than 0.02 m, such as less than 0.015 m. In an embodiment, the propagation distance between the second input transducer and the first input transducer is less than 0.3 m, such as less than 0.1 m, such as less than 0.08 m, e.g. less than 0.06 m, e.g. in the range between 0.02 and 0.1 m, e.g. in the range between 0.02 and 0.06 m. In an embodiment, the propagation distance between the second input transducer and the first input transducer is larger than 0.02 m, such as larger than 0.05 m, such as larger than 0.08 m, such as larger than 0.1 m, such as larger than 0.2 m.
The term ‘signal strength’ is taken to include signal level, signal power, and signal energy. In an embodiment, the signal strength detector comprises a level detector or a power spectrum detector. In an embodiment, ‘signal strength’ (e.g. at a specific frequency or range) refers to power spectrum density (e.g. at a specific frequency or range).
The first and second input transducers are intended to be located at the same ear of the user. In an embodiment, the first and second input transducers comprises first and second microphones, respectively.
In an embodiment, the first input transducer comprises (e.g. contains exactly) two input transducers.
In an embodiment, the hearing device comprises a BTE-part adapted to be worn at or behind an ear of a user, and an ITE-part adapted to be located at or in an ear canal of the user. In an embodiment, the first input transducer is located in the BTE-part. In an embodiment, the second input transducer is located in the ITE-part. In an embodiment, both ‘first input transducers’ are located in the BTE-part.
In an embodiment, the first input transducer is located in the BTE-part, and the second input transducer is located in the ITE-part.
In an embodiment, the hearing device comprises (e.g. consists of) two ‘first input transducers’ located in the BTE-part and one second input transducer located at or in an ear canal of the user, e.g. in the ITE-part.
In an embodiment, signal processing in the signal processing unit and/or in the feedback detector is performed in the time domain (on a broad band signal). In an embodiment, signal processing in the signal processing unit and/or in the feedback detector is performed in the time-frequency domain (in a number of frequency bands). In an embodiment, the signal processing in the signal processing unit is performed in the time-frequency domain, whereas the signal processing in the feedback detector is performed in the time domain (or in a smaller number of bands than in the signal processing unit). In an embodiment, the signal processing in the signal processing unit is performed in the time domain, whereas the signal processing in the feedback detector is performed in the time-frequency domain.
In an embodiment, the hearing device comprises a time to time-frequency conversion unit allowing the processing of signals in the (time-)frequency domain. In an embodiment, the time to time-frequency conversion unit comprises a filter bank or a Fourier transformation unit. In an embodiment, the comparison unit is configured to process the first and second electric input signal in a number of frequency bands. In an embodiment, the comparison unit is configured to only compare selected frequency bands, e.g. in correspondence with an acoustic transfer function from the second input transducer to the first input transducer. In an embodiment, the selected frequency bands are frequency bands that are estimated to be at risk of containing significant feedback, e.g. at risk of generating howl. In an embodiment, the selected frequency bands are predefined, e.g. determined in an adaptation procedure (e.g. a fitting session). In an embodiment, the selected frequency bands are dynamically determined, e.g. using a learning procedure (e.g. starting by considering all bands, and then limiting the comparison to bands where a significant level difference (e.g. above a predefined threshold level) is experienced over a predefined time period). In an embodiment, the feedback measure is provided in a number of frequency bands.
In an embodiment, the signal strength is taken to mean the magnitude (level) of the signal. In an embodiment, the decision unit is configured to apply a feedback difference threshold to make a binary distinction between a feedback dominant and non-feedback dominant acoustic situation. In an embodiment, a condition for concluding that a current acoustic situation is dominated by acoustic feedback is determined by the signal strength (e.g. the level or power or energy) of the second electric input signal being larger than the signal strength (e.g. the level or power or energy) of the first electric input signal AND the signal strength comparison measure indicative of the difference between the signal strength estimates being indicative of the difference being larger than the feedback difference threshold. In an embodiment, the feedback difference threshold is frequency dependent. In an embodiment, the feedback difference threshold is different in different frequency bands. The feedback difference threshold is preferably adapted in dependence on whether the signal strength is a level, a power or an energy. In an embodiment the feedback difference threshold is a threshold for the difference between the levels of the second and first electric input signals that discriminates between an acoustic situation with feedback (dominant feedback) and an acoustic situation with no feedback (not dominant feedback).
In an embodiment, the feedback difference threshold is predetermined. In an embodiment, the feedback threshold is determined during a fitting session, e.g. prior to the normal use of the hearing device. In an embodiment, the transfer function (e.g. the attenuation) of a sound source from the ear canal (e.g. the output transducer of the hearing device) from the second input transducer to the first input transducer is determined in an off-line procedure, e.g. during fitting of the hearing device to the specific user. In an embodiment, the transfer function from the second input transducer to the first input transducer is estimated in advance of the use of the hearing device, e.g. using an ‘average head model’, such as a head-and-torso simulator (e.g. Head and Torso Simulator (HATS) 4128C from Brüel & Kjæ Sound & Vibration Measurement A/S). In an embodiment, the transfer function from the second input transducer to the first input transducer is dynamically estimated. In an embodiment, the feedback difference threshold is between 5 dB and 25 dB. In an embodiment, the feedback difference threshold is adapted to represent a level difference between the first and second electric input signals. In an embodiment, the feedback difference threshold is between 15 dB and 25 dB. In an embodiment, the feedback difference threshold is larger than 15 dB, e.g. around 20 dB.
In an embodiment, the hearing device comprises a feedback cancellation system for reducing the acoustic or mechanical feedback from the output transducer to the first and/or second input transducer, and wherein the feedback measure indicative of the amount of acoustic feedback is used to control the feedback cancellation system. In an embodiment, the hearing device is configured to control an adaptation rate of an adaptive algorithm of the feedback cancellation system depending on the feedback measure. In an embodiment, the hearing device comprises a de-correlation unit for increasing a de-correlation between an output signal from the hearing device and an input signal to the hearing device (e.g. by introducing a small frequency shift, e.g. <20 Hz in the forward path of the hearing device). In an embodiment, the hearing device is configured to control the de-correlation unit (e.g. its activation or de-activation and/or the size of the frequency shift) depending on the feedback measure.
In an embodiment, the hearing device comprises a weighting unit comprising a mixer or a beamformer unit for providing a mixed or beamformed signal based on a weighted combination of said multitude of electric input signals or signals derived therefrom. In an embodiment, the weighting unit, e.g. the mixer or beamformer unit, is adapted to provide a weighted combination of the multitude of electric input signals. In an embodiment, one or more, such as all, of the weights is/are complex.
In an embodiment, the hearing device is configured to control the weighting unit, e.g. the mixer or beamformer unit, in dependence of the feedback measure. In an embodiment, one or more weights of the weighted combination of said multitude of electric input signals or signals derived therefrom is/are changed in dependence of the feedback measure. In an embodiment, the weights are changed to change an emphasis of the beamformer unit from one electric input signal to another in dependence of the feedback measure. In an embodiment, the weights of the beamformer unit are configured to emphasize the second electric input signal in case the feedback detector indicates that the current acoustic situation is NOT dominated by feedback. In an embodiment, the weights of the beamformer unit are configured to emphasize the first electric input signal(s) in case the feedback detector indicates that the current acoustic situation is dominated by feedback. In an embodiment, the hearing device is configured to change the weights of the beamformer unit to emphasize the first electric input signal(s) in the beamformed signal in case the feedback detector indicates that the current acoustic situation is dominated by feedback. In an embodiment, the hearing device is configured to change the weights of the beamformer unit from emphasizing the first electric input signal(s) towards emphasizing the second electric input signal in the beamformed signal in case the feedback detector changes its indication of the acoustic situation from being dominated by feedback to NOT being dominated by feedback.
In an embodiment, the hearing device is configured to control the beamformer unit to increase the weight of the first electric signal(s) in the beamformed signal in case the feedback difference indicates that the current acoustic situation is dominated by feedback. In an embodiment, the hearing device is configured to control the beamformer unit to increase the weight of the second electric signal in the beamformed signal in case the feedback difference indicates that the current acoustic situation is NOT dominated by feedback.
In an embodiment, the hearing device is configured to control the beamformer unit to increase the weight of the first electric signal(s) in the beamformed signal in frequency bands where the feedback difference indicates that the current acoustic situation is dominated by feedback. In an embodiment, the hearing device is configured to control the beamformer unit to decrease the weight of the second electric signal in the beamformed signal in frequency bands where the feedback difference indicates that the current acoustic situation is dominated by feedback. In an embodiment, the hearing device is configured to control the beamformer unit to increase the weight of the first electric signal(s) in the beamformed signal and to decrease the weight of the second electric signal in the beamformed signal in frequency bands where the feedback difference indicates that the current acoustic situation is dominated by feedback.
In an embodiment, the hearing device is configured to control the weighting unit (e.g. the mixer or the beamformer unit) to increase the weight of the first electric signal(s) and/or to decrease the weight of the second electric signal in the mixed or beamformed signal in frequency bands where the feedback difference indicates that the current acoustic situation is dominated by feedback.
In an embodiment, the signal processing unit is configured to take other measures than control of the beamformer unit in case of an indication by the feedback detector that the current acoustic situation is dominated by feedback. In an embodiment, such other measures may include changing a parameter of the feedback cancellation system, e.g. changing an adaptation rate of the adaptive algorithm and/or the application of a de-correlation (e.g. a frequency shift) to a signal of the forward path.
In an embodiment, the hearing device comprises a gain control unit. In an embodiment, the gain control unit form part of the signal processing unit. In an embodiment, the hearing device is configured to control the gain control unit in dependence of the feedback measure. In an embodiment, the gain control unit is configured to decrease the applied gain in case the feedback detector indicates that the current acoustic situation is dominated by feedback. In an embodiment, the hearing device comprises a gain control unit that is configured to allow separate gain regulation of the electric input signals from the different input transducers.
In an embodiment, the hearing device is configured to control a beamformer unit, a feedback cancellation system and/or a gain control unit according to a predefined criterion involving the feedback measure. In an embodiment, the predefined criterion involving the feedback measure comprises a lookup table of actions relating ranges of values of the feedback measure to actions related to the beamformer unit, the feedback cancellation system and the gain control unit.
In an embodiment, the hearing device comprises a hearing aid, a headset, an active ear protection device or a combination thereof.
In an embodiment, the hearing device is adapted to provide a frequency dependent gain and/or a level dependent compression and/or a transposition (with or without frequency compression) of one or frequency ranges to one or more other frequency ranges, e.g. to compensate for a hearing impairment of a user. In an embodiment, the hearing device comprises a signal processing unit for enhancing the input signals and providing a processed output signal.
In an embodiment, the output unit is configured to provide a stimulus perceived by the user as an acoustic signal based on a processed electric signal. In an embodiment, the output unit comprises a number of electrodes of a cochlear implant or a vibrator of a bone conducting hearing device. In an embodiment, the output unit comprises an output transducer. In an embodiment, the output transducer comprises a receiver (loudspeaker) for providing the stimulus as an acoustic signal to the user. In an embodiment, the output transducer comprises a vibrator for providing the stimulus as mechanical vibration of a skull bone to the user (e.g. in a bone-attached or bone-anchored hearing device).
In an embodiment, the input unit comprises a wireless receiver for receiving a wireless signal comprising sound and for providing an electric input signal representing said sound. In an embodiment, the hearing device comprises a directional microphone system adapted to enhance a target acoustic source among a multitude of acoustic sources in the local environment of the user wearing the hearing device. In an embodiment, the directional system is adapted to detect (such as adaptively detect) from which direction a particular part of the microphone signal originates.
In an embodiment, the hearing device comprises an antenna and transceiver circuitry for wirelessly receiving a direct electric input signal from another device, e.g. a communication device or another hearing device. In an embodiment, the hearing device comprises a (possibly standardized) electric interface (e.g. in the form of a connector) for receiving a wired direct electric input signal from another device, e.g. a communication device or another hearing device. In an embodiment, the direct electric input signal represents or comprises an audio signal and/or a control signal and/or an information signal. In an embodiment, the hearing device comprises demodulation circuitry for demodulating the received direct electric input to provide the direct electric input signal representing an audio signal and/or a control signal e.g. for setting an operational parameter (e.g. volume) and/or a processing parameter of the hearing device. In general, a wireless link established by a transmitter and antenna and transceiver circuitry of the hearing device can be of any type. In an embodiment, the wireless link is used under power constraints, e.g. in that the hearing device is or comprises a portable (typically battery driven) device. In an embodiment, the wireless link is a link based on (non-radiative) near-field communication, e.g. an inductive link based on an inductive coupling between antenna coils of transmitter and receiver parts. In another embodiment, the wireless link is based on far-field, electromagnetic radiation. In an embodiment, the communication via the wireless link is arranged according to a specific modulation scheme, e.g. an analogue modulation scheme, such as FM (frequency modulation) or AM (amplitude modulation) or PM (phase modulation), or a digital modulation scheme, such as ASK (amplitude shift keying), e.g. On-Off keying, FSK (frequency shift keying), PSK (phase shift keying), e.g. MSK (minimum shift keying), or QAM (quadrature amplitude modulation).
In an embodiment, the communication between the hearing device and the other device is in the base band (audio frequency range, e.g. between 0 and 20 kHz). Preferably, communication between the hearing device and the other device is based on some sort of modulation at frequencies above 100 kHz. Preferably, frequencies used to establish a communication link between the hearing device and the other device is below 50 GHz, e.g. located in a range from 50 MHz to 50 GHz, e.g. above 300 MHz, e.g. in an ISM range above 300 MHz, e.g. in the 900 MHz range or in the 2.4 GHz range or in the 5.8 GHz range or in the 60 GHz range (ISM=Industrial, Scientific and Medical, such standardized ranges being e.g. defined by the International Telecommunication Union, ITU). In an embodiment, the wireless link is based on a standardized or proprietary technology. In an embodiment, the wireless link is based on Bluetooth technology (e.g. Bluetooth Low-Energy technology).
In an embodiment, the hearing device has a maximum outer dimension of the order of 0.15 m (e.g. a handheld mobile telephone). In an embodiment, the hearing device has a maximum outer dimension of the order of 0.08 m (e.g. a head set). In an embodiment, the hearing device has a maximum outer dimension of the order of 0.04 m (e.g. a hearing instrument).
In an embodiment, the hearing device is portable device, e.g. a device comprising a local energy source, e.g. a battery, e.g. a rechargeable battery.
In an embodiment, the hearing device comprises a forward or signal path between an input transducer (microphone system and/or direct electric input (e.g. a wireless receiver)) and an output transducer. In an embodiment, the signal processing unit is located in the forward path between the input and output transducers. In an embodiment, the signal processing unit is adapted to provide a frequency dependent gain according to a user's particular needs. In an embodiment, the hearing device comprises an analysis path comprising functional components for analyzing the input signal (e.g. determining a level, a modulation, a type of signal, an acoustic feedback estimate, etc.). In an embodiment, some or all signal processing of the analysis path and/or the signal path is conducted in the frequency domain. In an embodiment, some or all signal processing of the analysis path and/or the signal path is conducted in the time domain.
In an embodiment, an analogue electric signal representing an acoustic signal is converted to a digital audio signal in an analogue-to-digital (AD) conversion process, where the analogue signal is sampled with a predefined sampling frequency or rate fs, fs being e.g. in the range from 8 kHz to 48 kHz (adapted to the particular needs of the application) to provide digital samples xn (or x[n]) at discrete points in time tn (or n), each audio sample representing the value of the acoustic signal at tn by a predefined number Nb of bits, Nb being e.g. in the range from 1 to 48 bits, e.g. 24 bits. A digital sample x has a length in time of 1/fs, e.g. 50 μs, for fs=20 kHz. In an embodiment, a number of audio samples are arranged in a time frame. In an embodiment, a time frame comprises 64 audio data samples (e.g. corresponding to a frame length of 3.2 ms). Other frame lengths may be used depending on the practical application.
In an embodiment, the hearing devices comprise an analogue-to-digital (AD) converter to digitize an analogue input with a predefined sampling rate, e.g. 20 kHz. In an embodiment, the hearing devices comprise a digital-to-analogue (DA) converter to convert a digital signal to an analogue output signal, e.g. for being presented to a user via an output transducer.
In an embodiment, the hearing device, e.g. the microphone unit, and or the transceiver unit comprise(s) a TF-conversion unit for providing a time-frequency representation of an input signal. In an embodiment, the time-frequency representation comprises an array or map of corresponding complex or real values of the signal in question in a particular time and frequency range. In an embodiment, the TF conversion unit comprises a filter bank for filtering a (time varying) input signal and providing a number of (time varying) output signals each comprising a distinct frequency range of the input signal. In an embodiment, the TF conversion unit comprises a Fourier transformation unit for converting a time variant input signal to a (time variant) signal in the frequency domain. In an embodiment, the frequency range considered by the hearing device from a minimum frequency fmin to a maximum frequency fmax comprises a part of the typical human audible frequency range from 20 Hz to 20 kHz, e.g. a part of the range from 20 Hz to 12 kHz. In an embodiment, a signal of the forward and/or analysis path of the hearing device is split into a number NI of (e.g. uniform) frequency bands, where NI is e.g. larger than 5, such as larger than 10, such as larger than 50, such as larger than 100, such as larger than 500. In an embodiment, the hearing device is/are adapted to process a signal of the forward and/or analysis path in a number NP of different frequency channels (NP≤NI). The frequency channels may be uniform or non-uniform in width (e.g. increasing in width with frequency), overlapping or non-overlapping.
In an embodiment, the hearing device comprises a number of detectors configured to provide status signals relating to a current physical environment of the hearing device (e.g. the current acoustic environment), and/or to a current state of the user wearing the hearing device, and/or to a current state or mode of operation of the hearing device. Alternatively or additionally, one or more detectors may form part of an external device in communication (e.g. wirelessly) with the hearing device. An external device may e.g. comprise another hearing device, a remote control, and audio delivery device, a telephone (e.g. a Smartphone), an external sensor, etc.
In an embodiment, one or more of the number of detectors operate(s) on the full band signal (time domain). In an embodiment, one or more of the number of detectors operate(s) on band split signals ((time-) frequency domain).
In an embodiment, the number of detectors comprises a level detector for estimating a current level of a signal of the forward path. In an embodiment, the predefined criterion comprises whether the current level of a signal of the forward path is above or below a given (L-)threshold value.
In a particular embodiment, the hearing device comprises a voice detector (VD) for determining whether or not an input signal comprises a voice signal (at a given point in time). A voice signal is in the present context taken to include a speech signal from a human being. It may also include other forms of utterances generated by the human speech system (e.g. singing). In an embodiment, the voice detector unit is adapted to classify a current acoustic environment of the user as a VOICE or NO-VOICE environment. This has the advantage that time segments of the electric microphone signal comprising human utterances (e.g. speech) in the user's environment can be identified, and thus separated from time segments only comprising other sound sources (e.g. artificially generated noise). In an embodiment, the voice detector is adapted to detect as a VOICE also the user's own voice. Alternatively, the voice detector is adapted to exclude a user's own voice from the detection of a VOICE.
In an embodiment, the hearing device comprises an own voice detector for detecting whether a given input sound (e.g. a voice) originates from the voice of the user of the system. In an embodiment, the microphone system of the hearing device is adapted to be able to differentiate between a user's own voice and another person's voice and possibly from NON-voice sounds.
In an embodiment, the hearing device comprises a classification unit configured to classify the current situation based on input signals from (at least some of) the detectors, and possibly other inputs as well. In the present context ‘a current situation’ is taken to be defined by one or more of
a) the physical environment (e.g. including the current electromagnetic environment, e.g. the occurrence of electromagnetic signals (e.g. comprising audio and/or control signals) intended or not intended for reception by the hearing device, or other properties of the current environment than acoustic;
b) the current acoustic situation (input level, feedback, etc.), and
c) the current mode or state of the user (movement, temperature, etc.);
d) the current mode or state of the hearing device (program selected, time elapsed since last user interaction, etc.) and/or of another device in communication with the hearing device.
In an embodiment, the hearing device comprises an acoustic (and/or mechanical) feedback suppression system. Acoustic feedback occurs because the output loudspeaker signal from an audio system providing amplification of a signal picked up by a microphone is partly returned to the microphone via an acoustic coupling through the air or other media. The part of the loudspeaker signal returned to the microphone is then re-amplified by the system before it is re-presented at the loudspeaker, and again returned to the microphone. As this cycle continues, the effect of acoustic feedback becomes audible as artifacts or even worse, howling, when the system becomes unstable. The problem appears typically when the microphone and the loudspeaker are placed closely together, as e.g. in hearing aids or other audio systems. Some other classic situations with feedback problem are telephony, public address systems, headsets, audio conference systems, etc. Adaptive feedback cancellation has the ability to track feedback path changes over time. It is based on a linear time invariant filter to estimate the feedback path but its filter weights are updated over time. The filter update may be calculated using stochastic gradient algorithms, including some form of the Least Mean Square (LMS) or the Normalized LMS (NLMS) algorithms. They both have the property to minimize the error signal in the mean square sense with the NLMS additionally normalizing the filter update with respect to the squared Euclidean norm of some reference signal.
In an embodiment, the hearing device further comprises other relevant functionality for the application in question, e.g. compression, noise reduction, etc.
In an embodiment, the hearing device comprises a listening device, e.g. a hearing aid, e.g. a hearing instrument, e.g. a hearing instrument adapted for being located at the ear or fully or partially in the ear canal of a user, e.g. a headset, an earphone, an ear protection device or a combination thereof.
Use:
In an aspect, use of a hearing device as described above, in the ‘detailed description of embodiments’ and in the claims, is moreover provided. In an embodiment, use is provided in a system or device comprising a microphone and a loudspeaker in sufficiently close proximity of each other to cause feedback from the loudspeaker to the microphone during operation by a user. In an embodiment, use is provided in a system comprising one or more hearing instruments, headsets, ear phones, active ear protection systems, etc., e.g. in handsfree telephone systems, teleconferencing systems, public address systems, karaoke systems, classroom amplification systems, etc.
A Hearing System:
In a further aspect, a hearing system comprising a hearing device as described above, in the ‘detailed description of embodiments’, and in the claims, AND an auxiliary device is moreover provided.
In an embodiment, the system is adapted to establish a communication link between the hearing device and the auxiliary device to provide that information (e.g. control and status signals, possibly audio signals) can be exchanged or forwarded from one to the other.
In an embodiment, the auxiliary device is or comprises an audio gateway device adapted for receiving a multitude of audio signals (e.g. from an entertainment device, e.g. a TV or a music player, a telephone apparatus, e.g. a mobile telephone or a computer, e.g. a PC) and adapted for selecting and/or combining an appropriate one of the received audio signals (or combination of signals) for transmission to the hearing device. In an embodiment, the auxiliary device is or comprises a remote control for controlling functionality and operation of the hearing device(s). In an embodiment, the function of a remote control is implemented in a SmartPhone, the SmartPhone possibly running an APP allowing to control the functionality of the audio processing device via the SmartPhone (the hearing device(s) comprising an appropriate wireless interface to the SmartPhone, e.g. based on Bluetooth or some other standardized or proprietary scheme).
In the present context, a SmartPhone (or similar device), may comprise
In an embodiment, the auxiliary device is another hearing device. In an embodiment, the hearing system comprises two hearing devices adapted to implement a binaural hearing system, e.g. a binaural hearing aid system.
The ‘near-field’ of an acoustic source is a region close to the source where the sound pressure and acoustic particle velocity are not in phase (wave fronts are not parallel). In the near-field, acoustic intensity can vary greatly with distance (compared to the far-field). The near-field is generally taken to be limited to a distance from the source equal to about a wavelength of sound. The wavelength λ of sound is given by λ=c/f, where c is the speed of sound in air (343 m/s, @ 20° C.) and f is frequency. At f=1 kHz, e.g., the wavelength of sound is 0.343 m (i.e. 34 cm). In the acoustic ‘far-field’, on the other hand, wave fronts are parallel and the sound field intensity decreases by 6 dB each time the distance from the source is doubled (inverse square law).
In the present context, a ‘hearing device’ refers to a device, such as e.g. a hearing instrument or an active ear-protection device or other audio processing device, which is adapted to improve, augment and/or protect the hearing capability of a user by receiving acoustic signals from the user's surroundings, generating corresponding audio signals, possibly modifying the audio signals and providing the possibly modified audio signals as audible signals to at least one of the user's ears. A ‘hearing device’ further refers to a device such as an earphone or a headset adapted to receive audio signals electronically, possibly modifying the audio signals and providing the possibly modified audio signals as audible signals to at least one of the user's ears. Such audible signals may e.g. be provided in the form of acoustic signals radiated into the user's outer ears, acoustic signals transferred as mechanical vibrations to the user's inner ears through the bone structure of the user's head and/or through parts of the middle ear as well as electric signals transferred directly or indirectly to the cochlear nerve of the user.
The hearing device may be configured to be worn in any known way, e.g. as a unit arranged behind the ear with a tube leading radiated acoustic signals into the ear canal or with a loudspeaker arranged close to or in the ear canal, as a unit entirely or partly arranged in the pinna and/or in the ear canal, as a unit attached to a fixture implanted into the skull bone, as an entirely or partly implanted unit, etc. The hearing device may comprise a single unit or several units communicating electronically with each other. The loudspeaker may be arranged in a housing together with other components of the hearing device, or may be an external unit in itself (possibly in combination with a flexible guiding element, e.g. a dome-like element).
More generally, a hearing device comprises an input transducer for receiving an acoustic signal from a user's surroundings and providing a corresponding input audio signal and/or a receiver for electronically (i.e. wired or wirelessly) receiving an input audio signal, a (typically configurable) signal processing circuit for processing the input audio signal and an output unit for providing an audible signal to the user in dependence on the processed audio signal. The signal processing unit may be adapted to process the input signal in the time domain or in a number of frequency bands. In some hearing devices, an amplifier and/or compressor may constitute the signal processing circuit. The signal processing circuit typically comprises one or more (integrated or separate) memory elements for executing programs and/or for storing parameters used (or potentially used) in the processing and/or for storing information relevant for the function of the hearing device and/or for storing information (e.g. processed information, e.g. provided by the signal processing circuit), e.g. for use in connection with an interface to a user and/or an interface to a programming device. In some hearing devices, the output unit may comprise an output transducer, such as e.g. a loudspeaker for providing an air-borne acoustic signal or a vibrator for providing a structure-borne or liquid-borne acoustic signal. In some hearing devices, the output unit may comprise one or more output electrodes for providing electric signals (e.g. a multi-electrode array for electrically stimulating the cochlear nerve).
In some hearing devices, the vibrator may be adapted to provide a structure-borne acoustic signal transcutaneously or percutaneously to the skull bone. In some hearing devices, the vibrator may be implanted in the middle ear and/or in the inner ear. In some hearing devices, the vibrator may be adapted to provide a structure-borne acoustic signal to a middle-ear bone and/or to the cochlea. In some hearing devices, the vibrator may be adapted to provide a liquid-borne acoustic signal to the cochlear liquid, e.g. through the oval window. In some hearing devices, the output electrodes may be implanted in the cochlea or on the inside of the skull bone and may be adapted to provide the electric signals to the hair cells of the cochlea, to one or more hearing nerves, to the auditory cortex and/or to other parts of the cerebral cortex.
A hearing device, e.g. a hearing aid, may be adapted to a particular user's needs, e.g. a hearing impairment. A configurable signal processing circuit of the hearing device may be adapted to apply a frequency and level dependent compressive amplification of an input signal. A customized frequency and level dependent gain may be determined in a fitting process by a fitting system based on a user's hearing data, e.g. an audiogram, using a fitting rationale. The frequency and level dependent gain may e.g. be embodied in processing parameters, e.g. uploaded to the hearing device via an interface to a programming device (fitting system), and used by a processing algorithm executed by the configurable signal processing circuit of the hearing device.
A ‘hearing system’ refers to a system comprising one or two hearing devices, and a ‘binaural hearing system’ refers to a system comprising two hearing devices and being adapted to cooperatively provide audible signals to both of the user's ears. Hearing systems or binaural hearing systems may further comprise one or more ‘auxiliary devices’, which communicate with the hearing device(s) and affect and/or benefit from the function of the hearing device(s). Auxiliary devices may be e.g. remote controls, audio gateway devices, mobile phones (e.g. SmartPhones), or music players. Hearing devices, hearing systems or binaural hearing systems may e.g. be used for compensating for a hearing-impaired person's loss of hearing capability, augmenting or protecting a normal-hearing person's hearing capability and/or conveying electronic audio signals to a person. Hearing devices or hearing systems may e.g. form part of or interact with public-address systems, active ear protection systems, handsfree telephone systems, car audio systems, entertainment (e.g. karaoke) systems, teleconferencing systems, classroom amplification systems, etc.
The aspects of the disclosure may be best understood from the following detailed description taken in conjunction with the accompanying figures. The figures are schematic and simplified for clarity, and they just show details to improve the understanding of the claims, while other details are left out. Throughout, the same reference numerals are used for identical or corresponding parts. The individual features of each aspect may each be combined with any or all features of the other aspects. These and other aspects, features and/or technical effect will be apparent from and elucidated with reference to the illustrations described hereinafter in which:
The figures are schematic and simplified for clarity, and they just show details which are essential to the understanding of the disclosure, while other details are left out. Throughout, the same reference signs are used for identical or corresponding parts.
Further scope of applicability of the present disclosure will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the disclosure, are given by way of illustration only. Other embodiments may become apparent to those skilled in the art from the following detailed description.
The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practised without these specific details. Several aspects of the apparatus are described by various blocks, functional units, modules, components, circuits, steps, processes, algorithms, etc. (collectively referred to as “elements”). Depending upon particular application, design constraints or other reasons, these elements may be implemented using electronic hardware, computer program, or any combination thereof.
The electronic hardware may include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. Computer program shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.
It is a general known problem for hearing aid users that acoustical feedback from the ear canal causes the hearing aid to whistle if the gain is too high and/or if the vent opening in the ear mould is too large. The more gain that is needed to compensate for the hearing loss, the smaller the vent (or effective vent area) must be to avoid whistle, and for severe hearing losses even the leakage between the ear mould (without any deliberate vent) and the ear canal can cause the whistling.
Hearing aids with microphones behind the ear can achieve the highest gain, due to their relatively large distance from the ear canal and vent in the mould. But for users with severe hearing loss needing high gain, it can be difficult to achieve a sufficient venting in the mould (with an acceptable howl risk).
An anti-feedback system may be designed to cancel out or attenuate the acoustical feedback. Such anti-feedback system (or ‘feedback cancellation system’) usually comprises some sort of howl- or tone-detection, and may act by suppressing the gain in case of a howl detection. Sometimes external sound are falsely identified as feedback howl, and then unintendedly suppressed. This may e.g. occur in the case of music (and be annoying to a listener).
EP2843971A1 deals with a hearing aid device comprising an “open fitting” providing ventilation, a receiver arranged in the ear canal, a directional microphone system comprising two microphones arranged in the ear canal at the same side of the receiver, and means for counteracting acoustic feedback on the basis of sound signals detected by the two microphones. An improved feedback reduction can thereby be achieved, while allowing a relatively large gain to be applied to the incoming signal.
The embodiment of
Each of the input transducers of the input unit (IUa, IUb) can theoretically be of any kind, such as comprising a microphone (e.g. a normal microphone or a vibration sensing bone conduction microphone), or an accelerometer, or a wireless receiver. The embodiments of a hearing device (HD) of
Each of the embodiments of a hearing device (HD) comprises an output unit (OU) comprising an output transducer (OT) for converting a processed output signal to a stimulus perceivable by the user as sound. In the embodiments of a hearing device (HD) of
The ‘operational connections’ between the functional elements signal processing unit (SPU), input transducers (IT1, IT2; IT11, IT12, IT2), and output transducer (OT)) of the hearing device (HD) can be implemented in any appropriate way allowing signals to the transferred (possibly exchanged) between the elements (at least to enable a forward path from the input transducers to the output transducer, via (and possibly in control of) the signal processing unit). The solid lines (denoted IN1, IN2, IN11, IN12, SS1, SS2, SS11, SS12, FBM, OUT) generally represent wired electric connections. The dashed zig-zag line (denoted WL in
The hearing device (here the signal processing unit) may e.g. further comprise a beamforming unit comprising a directional algorithm for providing an omni-directional signal or—in a particular DIR mode—a directional signal based on one or more of the electric input signals (IN1, IN2; or IN11, IN12, IN2). In such case, the signal processing unit (SPU) is configured to provide and further process a (spatially filtered) beamformed signal, and for providing a processed (preferably enhanced) output signal (OUT). In an embodiment, the feedback measure (FBM) is used as an input to the beamforming unit, e.g. to control or influence a mode of operation of the beamforming unit (e.g. between a directional and an omni-directional mode of operation, cf. e.g.
All embodiments of a hearing device are adapted for being arranged at least partly on a user's head or at least partly implanted in a user's head.
In the embodiment of a hearing device (HD) in
The hearing device (HD) further comprises an output unit (OT, e.g. an output transducer) providing an enhanced output signal as stimuli perceivable by the user as sound based on the enhanced audio signal from the signal processing unit or a signal derived therefrom. Alternatively or additionally, the enhanced audio signal from the signal processing unit may be further processed and/or transmitted to another device depending on the specific application scenario.
In the embodiment of a hearing device in
The hearing device of
The embodiment of a hearing device shown in
The signal processing unit (SPU) comprises e.g. a feedback cancellation system for reducing or cancelling feedback from the output transducer (OT) to the (second) input transducer (IT2) and/or to the (first) input transducer (IT1) of the BTE-part. The feedback cancellation system may preferably be controlled or influenced by the feedback measure.
The hearing device (HD) exemplified in
In an embodiment, the hearing device, e.g. a hearing aid (e.g. the signal processing unit SPU), is adapted to provide a frequency dependent gain and/or a level dependent compression and/or a transposition (with or without frequency compression) of one or frequency ranges to one or more other frequency ranges, e.g. to compensate for a hearing impairment of a user.
1st (BTE) and
2nd (ITE)
microphone
1st (BTE) and
signal level
2nd (ITE) microphone signal
differences
Time
Feedback
levels (upper plot, dash-dotted
(lower plot,
(seconds)
status
and solid lines, respectively)
solid line)
0-10
No
Both microphones at similar
Typically
feedback
levels, dominated by the target
<5
dB
incoming signal.
10-12
Strong
The ITE microphone signal has
Typically
feedback
a much higher level than the
>20
dB
BTE microphonesignal.
Especially the ITE microphone
signal is dominated by the
feedback signal.
12-20
Medium
The ITE microphone signal has
Typically
feedback
still higher level than the BTE
around
microphone signal.
5-10
dB
20-22
Strong
The ITE microphone signal has
Typically
feedback
a much higher level than the
>20
dB
BTE microphone signal.
Especially the ITE microphone
signal is dominated by the
feedback signal.
22-30
No
Both microphones at similar
<5
dB
feedback
levels, dominated by the target
incoming signal (far-field)
In the embodiment of
The hearing device, e.g. feedback detection unit (FBD), is configured to control the beamformer unit (BFU) and/or the gain control unit in dependence of the feedback measure (FBM). In an embodiment, one or more weights of the weighted combination of electric input signals IN1, IN2 or signals derived therefrom is/are changed in dependence of the feedback measure FBM, e.g. in that the weights of the beamformer unit are changed to change en emphasis of the beamformer unit from one electric input signal to another in dependence of the feedback measure. In an embodiment, the feedback detection unit (FBD) is configured to control the beamformer unit to increase the weight of the first electric signal IN1 in the beamformed signal BFS in case the feedback difference measure indicates that the current acoustic situation is dominated by feedback (e.g. |SS2−SS1|>FBTH, see e.g.
The hearing device, e.g. feedback detection unit (FBD), may further be configured to control the gain control unit in dependence of the feedback measure. In an embodiment, the hearing device is configured to decrease the applied gain based on an indication by the feedback detector that the current acoustic situation is dominated by feedback.
In the embodiment of
In
The embodiments of
In the embodiment of a hearing device shown in
The embodiment of
The embodiments of
The frequency (and time) dependent level differences Δ(f,t) between the input transducers (e.g. IT2 and IT1 of
As used, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well (i.e. to have the meaning “at least one”), unless expressly stated otherwise. It will be further understood that the terms “includes,” “comprises,” “including,” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will also be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element but an intervening elements may also be present, unless expressly stated otherwise. Furthermore, “connected” or “coupled” as used herein may include wirelessly connected or coupled. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
It should be appreciated that reference throughout this specification to “one embodiment” or “an embodiment” or “an aspect” or features included as “may” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Furthermore, the particular features, structures or characteristics may be combined as suitable in one or more embodiments of the disclosure. The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects.
The claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language of the claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” Unless specifically stated otherwise, the term “some” refers to one or more.
Accordingly, the scope should be judged in terms of the claims that follow.
Petersen, Svend Oscar, Guo, Meng, Thule, Anders
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